Comparative Study on Performances of Composite Anodes of SiO, Si and Graphite for Lithium Rechargeable Batteries

도칠훈,Angathevar Veluchamy,Duck-Jun Lee,Jung-Hoon Lee,진봉수,문성인,Cheol-Wan Park,김동원 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.5

The electrochemical performances of anode composites comprising elemental silicon (Si), silicon monoxide (SiO),and graphite (C) were investigated. The composite devoid of elemental silicon (SiO:C = 1:1) and its carbon coated composite showed reduced capacity degradation with measured values of 606 and 584 mAh/g at the fiftieth cycle. The capacity retention nature when the composites were cycled followed the order of Si:SiO:C = 3:1:4 < Si:SiO:C =2:2:4 < SiO:C = 1:1 < SiO:C = 1:1 (carbon coated). A comparison of the capacity retention properties for the composites in terms of the silicon content showed that a reduced silicon content increased the stability of the composite electrodes. Even though the carbon-coated composite delivered low capacity during cycling compared to the other composites, its low capacity degradation made the anode a better choice for lithium ion batteries.

Thermal Behavior of LixCoO2 Cathode and Disruption of Solid Electrolyte Interphase Film

도칠훈,Dong-Hun Kim,Jung-Hun Lee,Duck-Jun Lee,진봉수,김현수,문성인,황영기,Angathevar Veluchamy 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.4

Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and ion chromatography(IC) were employed to analyze the thermal behavior of LixCoO2 cathode material of lithium ion battery. The mass loss peaks appearing between 60 and 125 oC in TGA and the exothermic peaks with 4.9 and 7.0 J/g in DSC around 75 and 85 oC for the LixCoO2 cathodes of 4.20 and 4.35 V cells are explained based on disruption of solid electrolyte interphase (SEI) film. Low temperature induced HF formation through weak interaction between organic electrolyte and LiF is supposed to cause carbonate film disruption reaction, Li2CO3 + 2HF → 2LiF + CO2 + H2O. The different spectral DSC/TGA pattern for the cathode of 4.5 V cell has also been explained. Presence of ionic carbonate in the cathode has been identified by ion chromatography and LiF reported by early researchers has been used for explaining the film SEI disruption process. The absence of mass loss peak for the cathode washed with dimethyl carbonate (DMC) implies ionic nature of the film. The thermal behavior above 150 oC has also been analyzed and presented.

Reactivity of Li14P6S22 as a Potential Solid Electrolyte for All-Solid-State Lithium-Ion Batteries

도칠훈,하윤철,이유진,유지현 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.10

The electrochemical reactivity of Li14P6S22 (Li7P3S11) as a sulfur-based solid electrolyte for Li+ conduction was evaluated by electrochemical cell tests and ab initio calculations to determine its utility for all-solid-state lithium secondary batteries. Reversible removal and incorporation of lithium into Li14P6S22 with a gradient of lithium concentration was confirmed as thermodynamically unfavorable. Otherwise, reductive/oxidative decomposition of Li14P6S22 by the addition/removal of lithium was thermodynamically favorable. The electrochemical stability window (ESW) of Li14P6S22 was 0.429?V between 1.860 and 2.289?V (Li/Li+). The lowest potential of Li elimination was 2.289?V and occurred as oxidative decomposition. The highest potential of lithium addition was 1.860?V as reductive decomposition. Formation of Li14+xP6S22 and Li14?xP6S22 could be simultaneously achieved with reductive and oxidative decomposition by applying negative and positive over-potentials. The exposure of Li14P6S22 electrodes to positive and negative electric fields generated a large amount of irreversible specific capacity, which confirmed the oxidative and reductive decomposition. Considering the results of ab initio calculations on ESW and electrochemical cell tests, Li14P6S22 material should be protected from direct contact to the potential of cathode and anode so that it can appropriately serve as a solid electrolyte. The high Li+ conductivity of Li14P6S22 might originate from temporal (kinetic) and endurable formation of Frenkel defects resulting in a Li-deficient/excess composition of Li14P6S22.

고분자 도포를 이용한 실리콘-탄소의 합성 및 Si-C|Li Cell의 전기화학적 특성

도칠훈,정기영,진봉수,안계혁,민병철,최임구,박철완,이경직,문성인,윤문수,Doh, Chil-Hoon,Jeong, Ki-Young,Jin, Bong-Soo,An, Kay-Hyeok,Min, Byung-Chul,Choi, Im-Goo,Park, Chul-Wan,Lee, Kyeong-Jik,Moon, Seong-In,Yun, Mun-Soo 한국전기화학회 2006 한국전기화학회지 Vol.9 No.3

실리콘 분말에 polyaniline(PAn)을 중합하고 탄화하여 Si-C재료를 개발하고 물리적 특성 및 전기화학적 특성을 분석하였다. 평균입도는 PAn의 중합으로 증가하였으며 탄화로 일부 감소하였다. XRD분석으로 결정질의 실리콘과 비결정성의 탄소 재료가 공존함을 확인 하였다. Si-PAn 전구체로 부터 개발한 Si-C 재료를 이용한 Si-C|Li cell은 Si|Li cell에 비하여 우수한 특성을 나타내었으며, 탄소 전구체인 PAn의 HCl 탈도핑에 의해 전기화학적 특성을 개선할 수 있었다. 전해액 중 FEC 첨가한 경우 초기 방전 용량이 증가하였다. GISOC시험으로 구한 가역 비용량 범위는 Si-C(Si:PAn=50:50wt. ratio)|Li 전지의 경우 약 414mAh/g를 나타내었으며, 가역 범위에 대한 초기 충방전의 intercalation 효율(IIE)는 75.7%였으며, 표면 비가역 비용량은 35.4mAh/g을 나타내었다. Si-C composites were prepared by the carbonization of silicon powder covered by polyaniline(PAn). Physical and electrochemical properties of the Si-C composites were characterized by the particle size analysis, X-ray diffraction technique, scanning electron microscope, and electrochemical test of battery. The average particle size of the Si was increased by the coating of PAn and somewhat reduced by the carbonization to give silicone-carbon composites. XRD analysis' results were confirmed co-existence of crystalline silicon and amorphous-like carbon. SEM photos showed that the silicon particle were well covered with carbonacious materials depend on the PAn content. Si-C|Li cells were fabricated using the Si-C composites and were tested using the galvanostatic charge-discharge test. Si-C|Li cells gave better electrochemical properties than that of Si|Li cell. Si-C|Li cell using the Si-C from HCl undoped PAn Precursor showed better electrochemical properties than that from HCl doped PAn Precursor. Using the electrolyte containing FEC as an additive, the initial discharge capacity was increased. After that the galvanostatic charge-discharge test with the GISOC(gradual increasing of the state of charge) condition was carried out. Si-C(Si:PAn:50:50 wt. ratio)|Li cell showed 414 mAh/g of the reversible specific capacity, 75.7% of IIE(initial intercalation efficiency), 35.4 mAh/g of IICs(surface irreversible specific capacity).

유기전해액에서 루테늄산화물 전극의 전기화학적 특성

도칠훈,진봉수,문성인,윤문수,최상진,육경창,박정식,김상길,이주원,Doh, Chil-Hoon,Jin, Bong-Soo,Moon, Seong-In,Yun, Mun-Soo,Choi, Sang-Jin,Yug, Gyeong-Chang,Park, Jeong-Sik,Kim, Sang-Gil,Lee, Joo-Won 한국전기화학회 2003 한국전기화학회지 Vol.6 No.3

금속산화물 전극을 이용한 전기화학 캐패시터는 일반적으로 산성 수용액 전해질에서 금속산화물에 대한 양성자의 가역적인 전기화학반응을 이용한다. 수계 전해질을. 사용한 수퍼캐패시터는 전위창(electrochemical stability window)이 유기계 전해질을 사용한 수퍼캐패시터에 비해 좁은 문제를 안고 있다. 금속산화물 전극과 리튬 또는 암모늄 이온을 함유한 유기계 전해질을 사용한 전기화학 캐패시터의 특성을 확인하였다. $RuO_2$ 전극을 사용한 전기화학 캐패시터는 1M $LiPF_6$, EC, DEC 및 EMC혼합용매 전해액 중에서 순환전위전류법(주사속도. 2mV/sec, 전위영역: $2.0\~4.2V(Li|Li^+))$으로 산화 및 환원에 대하여 비정전용량을 구한 바, 각각 145 및 $142F/g-RuO_2{\cdot}nH_2O$이었다 Electrochemical capacitor made with metal oxide electrode uses rapid and reversible protonation/deprotonation of metal oxide material under the aqueous acidic solution, generally. Electrochemical stability window of aqueous electrolyte-type capacitor is narrow compared to that of organic electrolyte-type capacitor. Electrochemical characteristics of electrochemical capacitor made with metal oxide electrode and lithium or ammonium cation based organic electrolyte were evaluated. Electrochemical capacitor based on $RuO_2$ electrode material and 1M $LiPF_6$ in mixed solvents of EC, DEC, and EMC has anodic and cathodic specific capacitance of 145 and $142F/g-RuO_2{\cdot}nH_2O$, respectively, by using cyclic voltammetry with scan rate of 2mV/sec $g-RuO_2$ in potential range of $2.0\~4.2V(Li|Li^+))$.

충전상태에 따른 LiCoO₂ 전극소재의 열 특성

도칠훈,김동훈,신혜민,진봉수,김현수,문성인 한국공업화학회 2006 한국공업화학회 연구논문 초록집 Vol.2006 No.1

Effect of Silicon Content over Fe-Cu-Si/C Based Composite Anode for Lithium Ion Battery

도칠훈,진봉수,문성인,김현수,김기원,오대희,Hye-Min Shin,Dong-Hun Kim,Young-Dong Chung,벨루차미 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.2

Two different anode composite materials comprising of Fe, Cu and Si prepared using high energy ball milling (HEBM) were explored for their capacity and cycling behaviors. Prepared powder composites in the ratio Cu:Fe:Si = 1:1:2.5 and 1:1:3.5 were characterized through X-Ray diffraction (XRD) and scanning electron microscope (SEM). Nevertheless, the XRD shows absence of any new alloy/compound formation upon ball milling, the elements present in Cu(1)Fe(1)Si(2.5)/Graphite composite along with insito generated Li2O demonstrate a superior anodic behavior and delivers a reversible capacity of 340 mAh/g with a high coulombic efficiency (98%). The higher silicon content Cu(1)Fe(1)Si(3.5) along with graphite could not sustain capacity with cycling possibly due to ineffective buffer action of the anode constituents.

PC 비율에 따른 $LiPF_6/PC+EC+DEC$ 전해액의 물리적 특성 및 탄소분극과의 초기 전기화학적 특성

도칠훈,문성인,윤문수,Doh Chil-Hoon,Moon Seong-In,Yun Mun-Soo 한국전기화학회 2000 한국전기화학회지 Vol.3 No.4

흑연재료를 부극으로 사용하는 리튬2차전지의 유기 전해액으로 propylene carbonate(PC) 용매를 사용하면 흑연층간에 PC의 비가역적 삽입반응으로 인하여 흑연의 exfoliation이 진행된다. 유기전해액으로 ethylene carbonate(EC)를 사용하면 이러한 문제점은 해결되지만, EC의 어는점이 $36.2^{\circ}C$로 높은 것이 단점이다. EC계 전해액에 적정 비율의 PC를 첨가한 혼합 유기 전해액은 전도도가 향상 될 수 있으며, 흑연전극의 exfoliation도 감소시킬 수 있다. EC계 전해액에 첨가한 PC 함량에 따른 유전상수 및 몰전도도를 구하였으며, 동시에 탄소부극에 대한 전기화학적 특성을 조사하였다. $LiPF_6/EC+DEC$ 전해액에 첨가한 PC 함량이 증가하면 유전상수와 몰전도도는 직선적으로 증가하였다. 충방전 시험결과, MCMB-6-28s및 MPCF300의 비가역비용량은 첨가한 PC함량이 $0.83\%$인 경우에는 감소하였으나, 그 이후에는 PC함량에 따라 증가하였다 MPCF3000및 PCG100의 비가역비용량은 PC함량이 $10\%$까지는 50mAh/g이하였다. 그러나, 방전비용량은 첨가한 PC 함량과 관계없이 사용한 탄소재료에 따라서 일정한 값을 나타내었다. The exfoliation of graphite (layer) was progressed due to the irreversible insertion of PC molecules between graphene layers, when propylene carbonate (PC) solvent was used as the organic solvents. The problem could be mitigated by the replacement of PC by ethylene carbonate (EC). But, the freezing point of EC-based electrolyte increased due to the high freezing point of $EC(36.2^{\circ}C)$. Therefore, EC+PC mixed electrolyte is expected as a good organic electrolyte for lithium ion battery. The EC-based organic electrolyte containing PC within pertinent quantity can be expected to have high molar conductivity and reduced exfoliation of graphite layer. The dielectric constant and molar conductivity of $LiPF_6/PC+EC+DEC$ electrolyte was investigated with a variation in the PC content. The electrochemical properties of carbon electrode in the electrolyte were also investigated. Molar conductivity and dielectric constant increased linearly by increasing the PC volume fraction in the electrolyte. The results of charge-discharge test for carbon/electrolyte/Li cell indicated that the initial irreversible specific capacity(IIC) of MCMB-6-28s and MPCF3000 decreased by the addition of $0.83 vol\%$ of PC, but increased with PC content over than $0.83 vol\%$. In the case of MPCF3000 and PCG100 having less than $10 vol\%$ PC, IIC was lower than 50 mAh/g. The discharge specific capacities varied with carbon material, but did not vary with PC content in the electrolyte.

Structures and Formation Energies of Li_xC_6 (x=1-3) and its Homologues for Lithium Rechargeable Batteries

도칠훈,한병찬,진봉수,Hal-Bon Gu 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.6

Using first principles density functional theory the formation energies of various binary compounds of lithium graphite and its homologues were calculated. Lithium and graphite react to form Li_1C_6 (+141 mV) but not form LiC_4 (.143 mV), LiC_3 (.247 mV) and LiC_2 (.529 mV) because they are less stable than lithium metal itself. Properties of structure and reaction potentials of C_5B, C_5N and B_3N_3 materials as iso-structural graphite were studied. Boron and nitrogen substituted graphite and boron-nitrogen material as a iso-electronic structured graphitic material have longer graphene layer spacing than that of graphite. The layer spacing of Li_xC_6, Li_xC_5B,Li_xC_5N materials increased until to x=1, and then decreased until to x=2 and 3. Nevertheless Li_xB_3N_3 has opposite tendency of layer spacing variation. Among various lithium compositions of Li_xC_5B, Li_xC_5N and Li_xB_3N_3, reaction potentials of Li_xC_5B (x=1-3) and Li_xC_5 (x=1) from total energy analyses have positive values against lithium deposition.

배터리 앤트로피의 측정 방법과 응용

도칠훈,하윤철,엄승욱 한국표면공학회 2018 한국표면공학회 학술발표회 초록집 Vol.2018 No.11